Hi Tom,
there are hybrid modules combining solar heat gain with photovoltaic electricity production. They sound nice, beause photovoltaics needs low temperatures to work best. The
water used for solar heat gain, provides some cooling. Problem is, unless you have a huge demand for hot water, (Think swimming pool) on a good sunny day your heat storage is already hot and will heat the panels instead of cooling them. You
should really run your numbers, to determine how much hybrid and how much pure photovoltaic panels you need, to get your optimum.
regards
Ludger